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package org.meanzoft.m3d.texture;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.color.ColorSpace;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.ComponentColorModel;
import java.awt.image.DataBuffer;
import java.awt.image.DataBufferByte;
import java.awt.image.Raster;
import java.awt.image.WritableRaster;
import java.io.File;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.IntBuffer;
import java.util.HashMap;
import java.util.Hashtable;

import javax.imageio.ImageIO;
import org.lwjgl.opengl.GL11;
import org.lwjgl.opengl.GL12;

/**
 * A utility class to load textures for JOGL. This source is based
 * on a texture that can be found in the Java Gaming (www.javagaming.org)
 * Wiki. It has been simplified slightly for explicit 2D graphics use.
 *
 * OpenGL uses a particular image format. Since the images that are
 * loaded from disk may not match this format this loader introduces
 * a intermediate image which the source image is copied into. In turn,
 * this image is used as source for the OpenGL texture.
 *
 * @author Kevin Glass
 * @author Brian Matzon
 */
public class TextureLoader {

    /** The table of textures that have been loaded in this loader */
    private HashMap table = new HashMap();
    /** The colour model including alpha for the GL image */
    private ColorModel glAlphaColorModel;
    /** The colour model for the GL image */
    private ColorModel glColorModel;

    /**
     * Create a new texture loader based on the game panel
     *
     * @param gl The GL content in which the textures should be loaded
     */
    public TextureLoader() {
        glAlphaColorModel = new ComponentColorModel(ColorSpace.getInstance(ColorSpace.CS_sRGB),
                new int[]{8, 8, 8, 8},
                true,
                false,
                ComponentColorModel.TRANSLUCENT,
                DataBuffer.TYPE_BYTE);

        glColorModel = new ComponentColorModel(ColorSpace.getInstance(ColorSpace.CS_sRGB),
                new int[]{8, 8, 8, 0},
                false,
                false,
                ComponentColorModel.OPAQUE,
                DataBuffer.TYPE_BYTE);
    }

    /**
     * Create a new texture ID
     *
     * @return A new texture ID
     */
    public int createTextureID() {
        IntBuffer tmp = createIntBuffer(1);
        GL11.glGenTextures(tmp);
        return tmp.get(0);
    }

    /**
     * Load a texture
     *
     * @param resourceName The location of the resource to load
     * @return The loaded texture
     * @throws IOException Indicates a failure to access the resource
     */
    public Texture getTexture(String resourceName) throws IOException {
        Texture tex = (Texture) table.get(resourceName);

        if (tex != null) {
            return tex;
        }

        tex = getTexture(resourceName,
                GL11.GL_TEXTURE_2D, // target

                GL11.GL_RGBA, // dst pixel format

                GL11.GL_NEAREST, // min filter (unused)

                GL11.GL_NEAREST);
        
        table.put(resourceName, tex);

        return tex;
    }

    /**
     * Load a texture into OpenGL from a image reference on
     * disk.
     *
     * @param resourceName The location of the resource to load
     * @param target The GL target to load the texture against
     * @param dstPixelFormat The pixel format of the screen
     * @param minFilter The minimising filter
     * @param magFilter The magnification filter
     * @return The loaded texture
     * @throws IOException Indicates a failure to access the resource
     */
    public Texture getTexture(String resourceName,
            int target,
            int dstPixelFormat,
            int minFilter,
            int magFilter) throws IOException {
        int srcPixelFormat = 0;

        // create the texture ID for this texture

        int textureID = createTextureID();
        Texture texture = new Texture(resourceName, target, textureID);

        // bind this texture

        GL11.glBindTexture(target, textureID);

        BufferedImage bufferedImage = loadImage(resourceName);
        texture.setWidth(bufferedImage.getWidth());
        texture.setHeight(bufferedImage.getHeight());

        if (bufferedImage.getColorModel().hasAlpha()) {
            srcPixelFormat = GL11.GL_RGBA;
        } else {
            srcPixelFormat = GL11.GL_RGB;
        }

        // convert that image into a byte buffer of texture data

        ByteBuffer textureBuffer = convertImageData(bufferedImage, texture);

        if (target == GL11.GL_TEXTURE_2D) {
            GL11.glTexParameteri(target, GL11.GL_TEXTURE_MIN_FILTER, minFilter);
            GL11.glTexParameteri(target, GL11.GL_TEXTURE_MAG_FILTER, magFilter);
        }
        

        // produce a texture from the byte buffer

        GL11.glTexImage2D(target,
                0,
                dstPixelFormat,
                get2Fold(bufferedImage.getWidth()),
                get2Fold(bufferedImage.getHeight()),
                0,
                srcPixelFormat,
                GL11.GL_UNSIGNED_BYTE,
                textureBuffer);

        return texture;
    }

    /**
     * Get the closest greater power of 2 to the fold number
     *
     * @param fold The target number
     * @return The power of 2
     */
    public int get2Fold(int fold) {
        int ret = 2;
        while (ret < fold) {
            ret *= 2;
        }
        return ret;
    }

    /**
     * Convert the buffered image to a texture
     *
     * @param bufferedImage The image to convert to a texture
     * @param texture The texture to store the data into
     * @return A buffer containing the data
     */
    private ByteBuffer convertImageData(BufferedImage bufferedImage, Texture texture) {
        ByteBuffer imageBuffer = null;
        WritableRaster raster;
        BufferedImage texImage;

        int texWidth = 2;
        int texHeight = 2;

        // find the closest power of 2 for the width and height

        // of the produced texture

        while (texWidth < bufferedImage.getWidth()) {
            texWidth *= 2;
        }
        while (texHeight < bufferedImage.getHeight()) {
            texHeight *= 2;
        }

        texture.setTextureHeight(texHeight);
        texture.setTextureWidth(texWidth);

        // create a raster that can be used by OpenGL as a source

        // for a texture

        if (bufferedImage.getColorModel().hasAlpha()) {
            raster = Raster.createInterleavedRaster(DataBuffer.TYPE_BYTE, texWidth, texHeight, 4, null);
            texImage = new BufferedImage(glAlphaColorModel, raster, false, new Hashtable());
        } else {
            raster = Raster.createInterleavedRaster(DataBuffer.TYPE_BYTE, texWidth, texHeight, 3, null);
            texImage = new BufferedImage(glColorModel, raster, false, new Hashtable());
        }

        // copy the source image into the produced image

        Graphics g = texImage.getGraphics();
        g.setColor(new Color(0f, 0f, 0f, 0f));
        g.fillRect(0, 0, texWidth, texHeight);
        g.drawImage(bufferedImage, 0, 0, null);

        // build a byte buffer from the temporary image

        // that be used by OpenGL to produce a texture.

        byte[] data = ((DataBufferByte) texImage.getRaster().getDataBuffer()).getData();

        imageBuffer = ByteBuffer.allocateDirect(data.length);
        imageBuffer.order(ByteOrder.nativeOrder());
        imageBuffer.put(data, 0, data.length);
        imageBuffer.flip();

        return imageBuffer;
    }

    /**
     * Load a given resource as a buffered image
     *
     * @param ref The location of the resource to load
     * @return The loaded buffered image
     * @throws IOException Indicates a failure to find a resource
     */
    private BufferedImage loadImage(String ref) throws IOException {
        File f = new File(ref);

        if(!f.exists()) {
            throw new IOException("File not found " + ref);
        }

        BufferedImage bufferedImage = ImageIO.read(f);

        return bufferedImage;
    }

    /**
     * Creates an integer buffer to hold specified ints
     * - strictly a utility method
     *
     * @param size how many int to contain
     * @return created IntBuffer
     */
    protected IntBuffer createIntBuffer(int size) {
        ByteBuffer temp = ByteBuffer.allocateDirect(4 * size);
        temp.order(ByteOrder.nativeOrder());

        return temp.asIntBuffer();
    }
}
